Enzymes have been used for a long time for a variety of industrial applications. For instance the use of enzymes in detergents, both laundry and dishwashing detergents, has become increasingly popular in recent years. Further important uses of enzymes are in papermaking pulp processing, in the baking industry for improving the properties of flour, in the wine and juice industries for the degradation of .beta.-glucans, in the textile industry for bio-polishing of cellulosic fabrics such as viscose, i.e. for obtaining a soft and smooth fabric by subjecting the cellulosic fabrics to treatment by hemicellulolytic enzymes during their manufacture, and in animal feed for improving the digestibility of vegetable protein sources.
It is, however, far from easy to obtain an optimal enzyme performance e.g. in a detergent system, as the detergent formulation and washing conditions (for instance high pH, high ionic strength, and the inclusion of certain surfactants and builders) may have a crucial impact on the stability and activity of the enzyme.
Since washing conditions are quite often alkaline, some enzymes at least might be expected to show an improved performance if the pI of the enzymes is shifted to a value approximating that of the pH during application.
Similar considerations may apply to the use of enzymatic processes in other industries, e.g. one or more of the industries mentioned above.
E.g. when processing papermaking pulps, the lignocellulosic fibers may be subjected to enzymatic hydrolysis. Hydrolysing enzymes for fibre modification may be lipase for hydrolysis of triglycerides in pitch deposits, proteases for breakdown of structural proteins (e.g. extensin), and hemi-cellulase and pectinases for degradation of the carbohydrate material constituting the fibre wall.
It is well established that the effect e.g. of carbohydrases is limited due to electrostatic repulsion. So far no economical or technically feasible method for overcoming this limiting electrostatic repulsion has been suggested. In WO 93/11296 and WO 93/07332 it is described how the repulsion can be reduced by enzymatic removal of negatively charged glucoronic acid in the fibre matrix or by exchanging the counter ions on the acid groups in the fibre. These procedures are, however, very costly since bulk mass of lignocellulosic fibers must be treated with expensive specialty enzymes or metal salts. The latter may also cause problems in the internal water treatment of lignocellulosic fibre processing installations.
Furthermore, up till now it has been believed that the size of the enzyme molecules is another determining parameter for the effect of enzymes acting on lignocellulosic fibers. Average fibre pore sizes have been claimed to be of the same magnitude as the average diameter of the single enzyme molecules (Viikari, L., Kantelinen, A., Ratto, M. & Sundquist, J. (1991), Enzymes in Biomass Conversion, Chpt.2: Enzymes in Pulp and Paper Processing, p. 14, (Leatham, G. F. & Himmel, M. E., eds.). Thus, it is still an unsolved problem how to improve the effect of enzymatic hydrolysis of lignocellulosic fibers.